Conchoidal fracture [Was: stone identification ]

Fracture is conchoidal, What does this mean?

G’day: a conchoidal fracture is what you get when you break glass.

   / \
 /  /

/ /
/ /| \ @John_Burgess2
____ )
At sunny Nelson NZ (in mid- winter) and it’s a beaut day.

Conchoidal refers to a shell-like motif that is similar to the lined
surface (growth pattern) on the back of a sea shell. Refers to a fracture
on a gem material, and is most commonly seen on a piece of glass,
particularly the shell like appearance of a chip on the edge.